1. Field of the Invention
The present invention relates to the field of semiconductor manufacturing and more specifically to a method and apparatus for treating a deposited metal oxide dielectric film for interface control.
2. Discussion of Related Art
Integrated circuits are made up of literally millions of active and passive devices such as transistors, capacitors and resistors. In order to provide more computational power and/or more storage capability in an integrated circuit, device features are reduced or scaled down in order to provide higher packing density of devices. An important feature to enable scaling of devices is the ability to form high quality, high dielectric constant films for capacitor and gate dielectrics.
High dielectric constant films are generally ceramic films (i.e., metal-oxides) such as tantalum pentaoxide, titanium oxide, BST, and PZT. These films are generally deposited in the amorphous state by thermal chemical vapor deposition utilizing a metal organic precursor. Unfortunately, the use of metal organic precursors tend to incorporate carbon into the deposited oxide. Excess carbon is thought to lead to high leakage currents in metal oxide dielectrics. Traditionally a high temperature oxygen anneal is used to convert the metal oxide dielectric from the amorphous state to the polycrystalline state and to fill oxygen vacancies in the dielectric. Unfortunately, converting the amorphous metal dielectric to a polycrystalline dielectric in a high temperature oxygen anneal traps excess carbon in the dielectric film. Additionally, in the case of capacitors and MOS transistors, the high dielectric metal oxide film is normally formed on a silicon surface or a nitrided silicon surface, and the high temperature oxygen anneal can cause oxygen to diffuse through the dielectric and form undesired silicon dioxide at the metal oxide/silicon nitride and/or at the silicon nitride/poly interfaces. It is to be appreciated that silicon dioxide formation at these interfaces will create a low dielectric constant film in series with the high dielectric metal oxide film and therefore reduce the effective capacitance of the film.
Thus, what is desired is a method for converting an amorphous metal oxide dielectric into a polycrystalline metal oxide dielectric and for filling oxygen vacancies therein and to remove excess carbon without the formation of undesired silicon dioxide layers.